Originally published in the IPC Proceedings, the article “Effectiveness of Conformal Coat to Prevent Corrosion of Terminals“ was published online by circuit insight (http://www.circuitinsight.com/programs/54223.html). Author Michael Osterman is affiliated with the Center for Advanced Life Cycle Engineering, University of Maryland (College Park, MD).

The value of polymeric conformal coatings for protecting printed circuit boards (PCBs) from functional retardants like dust, corrosion, moisture, and temperature fluctuations is well-known. What may be less known is, that as the electrical components used in PCBs become smaller, traditional conformal films are commensurately less effective for certain coating purposes. With the rise of microelectricalmechanical systems (MEMS) and nano technology, nanocoats are increasing in prominence, in many cases surpassing even micro-thin parylene not-liquid coatings in utility for MEMS/nano applications.

Conformal coating of an object occurs when an appropriate coating material is applied on-top and around an underlying substrate, to protect it from such environmental and performance concerns as chemical incursion and excess moisture. Liquid organic polymer conformal coatings – acrylic, epoxy, silicone and urethane – prevent:

Liquid conformal coatings provide inexpensive, easily-applied insulative protection for printed circuit boards (PCBs) and similar electronics. However, the films’ otherwise desirable insulative qualities can interfere with operation of the assemblies’ electrical components, items like capacitors, connectors, diodes, resistors, or transistors, if these are coated. Liquid coatings are designed to "wick" under components and in between connectors to provide a complete coat, through brushing, dip-immersion, or spraying. These methods work exceptionally well, rendering an overall, dielectric conformal film for the PCB.